1. Field of Invention
The present invention relates to an electro-optical device using an electro-optical element whose brightness is controlled by a current, a method of driving the electro-optical device, and an electronic apparatus. More particularly, the present invention relates to a technology for interrupting a current path for a driving current.
2. Description of Related Art
Recently, flat panel displays (FPDS) using organic EL (electroluminescence) elements are of high interest. An organic EL element is a typical current-driven element which is driven by a current flowing therein, and emits light with a brightness corresponding to the current level. Driving methods for active-matrix displays using organic EL elements are roughly grouped into a voltage-programmed type and a current-programmed type.
As an example, Japanese Unexamined Patent Application Publication No. 2001-60076 discloses a voltage-programmed pixel circuit having a transistor (TFT3 shown in FIG. 5 of this document) in a current path for supplying a driving current to an organic EL element so as to interrupt the path. The transistor is turned on in the first half of one frame period, and is turned off in the last half thereof. Thus, for the first half period in which the transistor is turned on to let the driving current flow, the organic EL element emits light with a brightness corresponding to the current level. For the last half period in which the transistor is turned off to interrupt the driving current, the organic EL element is forcibly extinguished and is displayed as black. This technique is called blinking, and the blinking technique allows an after image left in the human eye to be stopped, thus improving the display quality of moving pictures.
As other examples, Japanese Unexamined Patent Application Publication No. 2001-147659 and Japanese Unexamined Patent Application Publication No. 2002-514320 disclose current-programmed pixel circuit structures. Japanese Unexamined Patent Application Publication No. 2001-147659 refers to a pixel circuit using a current mirror circuit formed of a pair of transistors. Japanese Unexamined Patent Application Publication No. 2002-514320 refers to a pixel circuit that reduces current nonuniformity and threshold voltage variations in drive transistors as sources that set the driving current supplied to organic EL elements.